in my application i have a side bar and a bottom bar and a lot of windows(~50 window), the side bar is used to navigate between windows.
the problem that i want the side bar and the bottom bar to be fixed at their place when navigating between windows + i want the child window to appear inside the parent window (resize and move with the parent window) , what is the Xojo way of doing it?
There is not way of doing true MDI windows on a Mac at all. It has never really been a thing on Mac. The Mac windowing system does not support real windows being bound inside a parent window. Applications like Photoshop simulate this using their own “window” system.
Typically an application like that on Mac would use floating palets for the navigation and side bars.
You could possibly achieve this by converting all of your windows to container controls and embed the relevant container control into the window containing the side bar and bottom bar.